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View Full Version : Distance and Speed calcualtions


mglavin58
Jan 21, 2007, 07:54 PM
I'm trying to calculate the speed variables with a given travel arc at differing arm lengths.

For example the fixed/known speed is 60 degrees travel is .10 seconds with a 1" arm or pivot point spacing from center, the speed (0.10 seconds) and travel arc (60 degrees) remain a constant.

What formula could be used to factor the travel arc speed with a .5" and a 2.0" arm? Is it as simple as dividing the speed by the arm length?

S = d/t is incomplete, the wrong formula or maybe I have to solve something first?

Ultimately I would like to calculate the speed realized from a driven arm or lever of various lengths. The driver would be the 1” arm noted above or a variable thereof with the constants named. The driven would be an arm or a lever of various lengths or ratio, for instance a .5” arm driving a 2” lever with a ratio of 4:1. Obviously mechanical advantage is in play and the 4:1 ratio limits the driven components travel arc to approximately 15 degrees.

Thanks in advance
Michael

Capuchin
Jan 22, 2007, 12:43 AM
Some of the things you state are confusing, and I'm unsure of what you're asking.

From what I gather you are moving a 1" arm through 60 degrees, and it takes 0.10 seconds.

I don't see why this would change for a different arm length without knowing the specs of the motor you're using to rotate it. It would have to apply more torque to a longer arm, but I don't know if the motor is running at it's limits, or if it's just running at a certain speed.

You say that the speed remains constant, and then state you want to find the new speed with a different length arm... but you just said the speed is constant...

Do you mean the speed of the end of the arm?

Please reply and I'll do all I can to help

mglavin58
Jan 22, 2007, 12:58 AM
Yes, I'm talking about the speed at the end of the arm, specifically it's the arms pivot point... And yes the speed is constant at center of the arm or source. Specifications suggest .10s was/is measured with a 1" space between the arms pivot points end to end traveling 60 degrees..

Capuchin
Jan 22, 2007, 01:01 AM
Okay, so yes, the 2" arm will move twice as fast, and the 0.5" will move half as fast at the end

I dislike you quoting a speed as "0.10 seconds" speed is measured in meters per second, although I see what you mean is 60 degrees in 0.10 seconds, which is 600 degrees per second. (angular velocity)

It is this angular velocity that is constant

You can work out the distance that a point has moved by working out the circumference of the circle it is on.

The 1" arm moves 2*pi*1*60/360 inches, the 2" moves 2*pi*2*60/360 inches and the 0.5" arm moves 2*pi*0.5*60/360 inches, and each does it in 0.1 seconds

Hope this helps